The subject matter disclosed herein relates to the art of steam turbomachines and, more particularly, to a butterfly plate for a steam turbomachine hood.
Many power generation facilities employ steam turbomachine systems having a low pressure (LP) steam turbine portion coupled to an intermediate pressure (IP) steam turbine portion and a high pressure (HP) steam turbine portion to drive a generator. In general, steam is expanded in the LP steam turbine portion and channeled into an exhaust hood. The exhaust hood separates steam under vacuum from atmospheric conditions, while providing support to rotating and stationary turbomachinery. Generally, stationary components direct steam toward rotating components to facilitate rotor rotation that is employed in power generation. Also, exhaust hoods provide static pressure recovery that allows for additional expansion of gases passing to last stage turbine buckets.
An exemplary exhaust hood is formed from various complex sheet metal plates that are combined to form a shell assembly. The shell assembly is machined to provide connections for internal and external components. The shell assembly includes upper and lower halves that guide steam downward toward a condenser. The exhaust hood includes a butterfly plate that turns an upper steam flow 180° downward toward the condenser. Existing butterfly plates include both linear and elliptical cross-sectional profiles that are formed to turn the upper steam flow vertically downward.